A vast number of commercial products that are difficult to produce synthetically are today produced by fermenting organisms. Such products include alcohols (e.g., ethanol, methanol, butanol, 1,3-propanediol); organic acids (e.g., citric acid, acetic acid, itaconic acid, lactic acid, gluconic acid, gluconate, lactic acid, succinic acid, 2,5-diketo-D-gluconic acid); ketones (e.g., acetone); amino acids (e.g., glutamic acid); gases (e.g., H2 and CO2), and more complex compounds, including, for example, antibiotics (e.g., penicillin and tetracycline); enzymes; vitamins (e.g., riboflavin, B12, beta-carotene); and hormones. Fermentation is also commonly used in the consumable alcohol (e.g., beer and wine), dairy (e.g., in the production of yogurt and cheese), leather, and tobacco industries.
A vast number of processes of producing fermentation products, such as ethanol, by fermentation of sugars provided by degradation of starch-containing material are known in the art.
However, production of fermentation products, such as ethanol, from such plant materials is still too costly. Therefore, there is a need for providing processes that can increase the yield of the fermentation product and thereby reducing the production costs.
WO 2008/049615 discloses the use of vitamins in a fermentation process for the production of, e.g., amino acids or ethanol, wherein at least 4 vitamins selected from the group consisting of: thiamine, cobalamine, riboflavine, niacinamide, pantothenic acid, biotin, ascorbic acid, retinol, procalciol, tocopherol, folic acid and pyridoxamine are used, and wherein the use of these vitamins enhances the bacterial growth rate at least by 50 percent and the product concentration at least by 10 percent compared to a reference fermentation process, performed without adding vitamins.
Corzo-Marinez et al. (J. Agric. Food. Chem. 58(1):500-6 (2010)) disclose that pyridoxamine has an inhibitory effect of on the initial stages of the Maillard reaction during the formation of conjugates of beta-lactoglobulin with galactose and tagatose.
Voziyan et al. (Cell Mol. Life. Sci. 62(15): 1671-1681 (2005)) disclose that pyridoxamine can inhibit glycation reactions and the formation of advanced glycation end products (AGEs). The mechanism of action of pyridoxamine includes inhibition of AGE formation by blocking oxidative degradation of the Amadori intermediate of the Maillard reaction.
Metz et al. (Arch. Biochem. Biophys. 419(1): 41-49 (2003)) disclose that pyridoxamine inhibits the formation of advanced lipoxidation end-products on protein during lipid peroxidation reactions, and has a strong lipid-lowering effect in streptozotocin-induced diabetic and Zucker obese rats, and protects against the development of nephropathy in both animal models.
Voziyan et al. (NY Acad. Sci. 1043: 807-816 (2005)) disclose that pyridoxamine is a critical transient intermediate in catalysis of transamination reactions by vitamin B6-dependent enzymes.
Sato et al. (Appl. Environ. Microbiol. 58(2): 734-736 (1992)) disclose that the addition of yeast extract, a vitamin mixture containing vitamin B(12), biotin, pyridoxamine, and p-aminobenzoic acid enhanced formation of ethanol but decreased lactate production in the fermentation of cellulose by Clostridium thermocellum. 
It is an object of the present invention to provide an improved process for producing a fermentation product.